Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/1999
Publication Date: N/A
Citation: Interpretive Summary: Atmospheric concentrations of carbon dioxide (CO2) and ozone (O3) are increasing. Variations in CO2 concentrations have generally increased crop growth and yields. Chronic exposure to high ozone causes leaf injury and generally reduces crop growth and yields. Moderate drought reduces gas exchange and may reduce crop sensitivity to ozone. Crop responses to these gases have been studied individually. The main objective of this study was to evaluate the combined effects of soil moisture, CO2, and ozone on leaf area index (LAI), biomass, and yield of soft red winter wheat cultivars. Wheat was grown in large open top chambers with two soil moisture levels and four air quality treatments (ambient and elevated CO2 and O3). Leaf area index biomass and grain yield were reduced by the addition of ozone. Elevated CO2 compensated for the reductions in yields caused by high ozone. The productivity of the wheat cultivars to air quality treatments did not change radically under reduced water availability.
Technical Abstract: Our objective was to examine yield and plant biomass responses among two soft red winter wheat cultivars to CO2, O3, and soil moisture treatments. From 1995 to 1997, wheat was grown in three meter diameter open top chambers at Beltsville, MD. Two soil moisture regimes were applied: well watered (WW) and restricted moisture (RM). Four air quality treatments were applied: charcoal filtered air (CF); CF with addition of approx. 150 uL CO2 L-1 (CF+CO2); non-filtered air with addition of approx. 35 nL O3 L-1 (NF+O3); and NF with addition of both CO2 and O3 (NF+CO2+O3). The two cultivars were Gore, a dwarf cultivar from Georgia, and Susquehanna, a tall cultivar from Maryland. Leaf area index was more sensitive to O3 treatments than to CO2 levels under WW conditions, with responses being similar but non significant under RM conditions. Yield components were mostly influenced by O3; strong trends indicate lower total dry biomass for plants exposed to high O3 for either cultivar and soil moisture regime. Grain yields were decreased by high O3 in most cases. Compensation by elevated CO2 for reductions caused by O3 exposures were observed which resulted in grain yields under NF+CO2+O3 generally equivalent to CF. Ozone induced yield reductions were often dependent on the mass per grain and less on the number of grain per unit area. Results from this study showed that the productivity of wheat cultivars in response to air quality treatments did not change radically under differential levels of water availability. Inferences from these results must be realized cautiously in order to model or predict the productivity of wheat crops to differential levels of CO2, O3, and H2O.